In a portable-type operating machine, such as a chain saw, which has an internal combustion engine as its driving means, an air cleaner, which cleans the air sucked into the machine from outside before it is conveyed to the carburetor, is generally arranged in the machine at a position that is in the vicinity of the carburetor. The trouble with this type of conventional air cleaner is that its overall construction is relatively complicated, with the number of parts being rather large. In addition, the operation of mounting it on the machine body and its maintenance have been rather bothersome. Furthermore, the machine is subject to dust contamination while the air cleaner is detached from the machine.